Conveying device

ABSTRACT

A conveying device in which a conveying arm assembly can be quickly set in a conveying position and can be rapidly stabilized in the conveying position is disclosed. The conveying device comprises a conveying arm assembly, a fixed shaft, at least one set of hollow operating shafts which are necessary for controlling an operation of the conveying arm assembly, and a motor provided between the fixed shaft and each of the operating shafts. The one set of operating shafts are attached to the fixed shaft such that they can be rotated coaxially with respect to the fixed shaft outside fixed shaft and are arranged in an axial direction of the fixed shaft. The motor comprises a stator provided on the fixed shaft and a rotor provided on each of the operating shafts such that it is opposed to the stator on an outer peripheral side of the stator.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a conveying device for conveying a workpiece such as a silicon wafer, for example.

2. Description of the Related Art

For etching of a wafer, CVD (chemical vapor deposition) and the like,for example, it is necessary to convey the wafer in a multi-chamber in aclean and ultra-high vacuum environment. In such an environment, theconveying device operates. A conveying device which does not require theuse of a magnetic fluid seal, that is, a conveying device provided witha separating wall between a rotor and a stator in a motor has beendevised in order to prevent the environment in the chamber from beingdeteriorated. The conveying devices described in Japanese Patent No.2,761,438 and U.S. Pat. No. 5,720,590 are examples of such conveyingdevices. FIG. 9 is a longitudinal sectional view showing a conveyingdevice 101 having the same basic structure as the conveying devicesdescribed in the above-mentioned publications. The conveying device 101comprises a coaxial shaft mechanism including a first shaft 121 and asecond shaft 122 which are independently rotatable, and a conveying armassembly 130 fixed to the upper ends of the shafts 121 and 122. Thefirst shaft 121 extends downward from the lower end of the second shaft122 and penetrates the second shaft 122. A rotor R′ is attached to theouter peripheral sides of the first shaft 121 and the second shaft 122,and a stator S′ is attached to a housing 190 accommodating the firstshaft 121 and the second shaft 122. A motor M′ is constituted by therotor R′ and the stator S′. By controlling the rotation of the motor M′,the expansion, contraction and turn of the conveying arm assembly 130can be controlled. The reference numeral 145 denotes an optical encoderfor detecting the rotation of the first and second shafts 121 and 122.

In the conveying device 101 having such a structure, it is required thatthe conveying arm assembly 130 should be quickly set in a conveyingposition and be rapidly stabilized in the conveying position. For thispurpose, adequate characteristics are required for the shafts 121 and122. FIG. 10 is a chart showing a process of controlling the rotation ofthe shaft, wherein an axis of ordinate indicates angular velocity of theshaft and an axis of abscissa indicates time. In general, the rotationof the shaft is controlled to reach a stopping step “e” from a stoppingstep “a” through an accelerating step “b”, a constant-velocity rotatingstep “c” and a decelerating step “d” as shown in FIG. 10. In theconveying device 101, it is necessary to rapidly accelerate ordecelerate the shafts 121 and 122, that is, to increase an angularacceleration at the accelerating step “b” and an angular decelerationthe decelerating step “d” shown in FIG. 10 in order to quickly set theconveying arm assembly 130 in the conveying position. Moreover, theoscillation of the angular velocity is observed in the early stage ofthe constant-velocity rotating step “c” and that of the stopping stage“e” in FIG. 10. In order to quickly stabilize the conveying arm assembly130 in the conveying position, however, it is necessary to reduce timest1 and t2 taken to cause the oscillated angular velocity to converge ona constant value, that is, stabilizing times. With an increase in thesize of the work piece, furthermore, the conveying device should havethe characteristics that a conveying distance is long and the conveyingdevice is resistant to a great load. In order to satisfy theserequirements, the torsional rigidity of each of the shafts 121 and 122should be increased. If it is desired to increase the torsional rigidityof each of the shafts 121 and 122, it is necessary to shorten the shafts121 and 122 or to increase a modulus of section of each of the shafts121 and 122.

Moreover, when the conveying arm assembly 130 connected to the twoshafts 121 and 122 is to be driven, the synchronous driving of the twoshafts 121 and 122 is required. For this purpose, it is necessary toreduce a difference in the torsional rigidity between the two shafts 121and 122. In order to reduce the difference in the torsional rigiditybetween the two shafts 121 and 122, it is necessary to reduce adifference in a length between the two shafts 121 and 122 and adifference in a modulus of section between the shafts 121 and 122.

In the conveying device 101, however, the first shaft 121 extendsdownward from the lower end of the second shaft 122 to penetrate thesecond shaft 122. For this reason, particularly, it is hard to reducethe length of the inside shaft 121 and to increase an outside diameterthereof. If the outside diameter is increased, the inside and outsidediameters of the second shaft 122 should also be increased.Consequently, the outside dimensions and weights of both the shafts 121and 122 are increased. Therefore, a large-sized motor is required forcontrolling the expansion, contraction and turn of the conveying armassembly 130. Moreover, it is impossible to avoid an increase in theoutside diameter of the housing 190.

With the structure of the conveying device 101, furthermore, the shaft121 has a greater length and a smaller modulus of section than the shaft122. Therefore, the difference in the torsional rigidity between boththe shafts 121 and 122 is great. Accordingly, both the shafts 121 and122 cannot be synchronously driven by rapid acceleration anddeceleration.

In order to perform positioning with high precision, run-out of theshaft should be small. In the conveying device 101, the run-out isgenerated on the shaft 122 due to the precision of a bearing 100B duringthe rotation thereof. Similarly, when the shaft 121 is relativelyrotated with respect to the shaft 122, relative run-out is generated onthe shaft 121 with respect to the shaft 122 due to the precision of abearing 100B′. In the conveying device 101, therefore, when the shaft121 and the shaft 122 are rotated at the same time, accumulative run-outis generated on the shaft 121 due to the precision of each of thebearings 100B and 100B′. Consequently, it is impossible to perform thepositioning with high precision.

The conveying device 101 has such a structure that the operation of oneconveying arm assembly 130 is controlled by a set of shafts 121 and 122.If the operations of a plurality of conveying arm assemblies are to becontrolled by plural sets of shafts, the above-mentioned problems becomemore remarkable. For example, if two conveying arm assemblies are to becontrolled by two sets of shafts, four shafts are coaxially provided tocontrol the operation of one of the conveying arm assemblies by means oftwo inner shafts and that of the other conveying arm assembly by meansof two outer shafts. With such a structure, it is harder to reduce thelength of the inner shaft and to increase the modulus of sectionthereof. Furthermore, the torsional rigidity of the inner shaft cannotbe increased. Moreover, the lengths and moduli of section of innermostand outermost shafts have very great differences. Therefore, adifference in the torsional rigidity becomes very great. In particular,the innermost shaft is attached to the housing through much morebearings. Therefore, the accumulation of the run-out due to theprecision of the bearing is increased so that the run-out becomes verygreat, resulting in poor positioning precision.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a conveying devicein which the torsional rigidity of a shaft can be enhanced withoutincreasing the dimension of the conveying device and a difference in thetorsional rigidity between a plurality of shafts can be reduced, andfurthermore, run-out due to the precision of a bearing is notaccumulated.

The present invention provides a conveying device comprising a conveyingarm assembly, a fixed shaft, at least one set of hollow operating shaftswhich are necessary for controlling an operation of the conveying armassembly, and a motor provided between the fixed shaft and each of theoperating shafts. The one set of operating shafts are attached to thefixed shaft such that they can be rotated coaxially with respect to thefixed shaft on an outside of the fixed shaft and are arranged in anaxial direction of the fixed shaft. The motor comprises a statorprovided on the fixed shaft and a rotor provided on each of theoperating shafts such that it is opposed to the stator on an outside ofthe stator. Thus, the operating shafts are provided on the outside ofthe fixed shaft. Consequently, the outside diameters and moduli ofsection of the operating shafts are increased. Even if the outsidediameters are increased, the weights are comparatively small because theoperating shafts have hollow structures and annular cross-sections.Moreover, it is not necessary for one of the operating shafts topenetrate the other operating shaft. Therefore, both the operatingshafts can be shortened. Thus, the torsional rigidity of the operatingshaft can be enhanced without increasing the dimension of the conveyingdevice.

In addition, the lengths and cross-sectional shapes of both theoperating shafts can be set almost identically. A difference in thetorsional rigidity between both the operating shafts can be reduced.

Thus, the torsional rigidity of the operating shaft can be enhancedwithout increasing the dimension of the conveying device. Therefore, theoperating shaft can be rapidly accelerated and decelerated. In addition,synchronous driving can be performed at a high speed by reducing adifference in the torsional rigidity between a plurality of operatingshafts. Consequently, the conveying arm assembly can be quickly set inthe conveying position. Furthermore, even if the angular velocity of theoperating shaft is oscillated, it rapidly converges. Therefore, it ispossible to reduce a time taken for stabilizing the conveying armassembly in the conveying position. As a result, a work for setting theconveying arm assembly in the conveying position can be rapidlyperformed.

Moreover, a bearing can generally be used for rotatably holding theoperating shafts. Each of the operating shafts are not held through abearing attached to the other operating shaft but are directly held bymeans of a bearing attached to the fixed shaft. Therefore, run-out canbe reduced without the accumulation of the run-out of the operatingshaft.

Furthermore, the rotor which serves as a point of action of the motor issituated in a point which is more distant from the center of rotation.Therefore, it is possible to obtain a necessary torque even if theheight of the rotor is reduced. Accordingly, the torsional rigidity canbe increased by shortening the operating shaft. In addition, the heightof the conveying device can also be reduced.

The torsional rigidity of the operating shaft is increased.Consequently, a resonance frequency can be more increased than afrequency included in a motor driving signal. Thus, a resonance can beavoided.

The above-mentioned conveying device may further comprise a plurality ofconveying arm assemblies and plural sets of operating shafts forcontrolling operations of the conveying arm assemblies. Even if thenumber of the operating shafts is increased by such a structure, theoutside diameters of the operating shafts do not need to be reduced andtheir torsional rigidities can be kept great. Moreover, even if thenumber of the operating shafts is increased, the cross-sectional shapesof all the operating shafts can be set almost identically. Consequently,a difference in the torsional rigidity can be reduced. Furthermore, evenif the number of the operating shafts is increased, respective bearingscan be all attached to the fixed shaft. Therefore, the run-outs of allthe operating shafts can be reduced almost identically.

In the above-mentioned conveying device, furthermore, a rotationdetecting portion capable of detecting rotation of the operating shaftmay be provided between the fixed shaft and the operating shaft. Therotation detecting portion may be constituted by a resolver typeposition detector or an optical encoder, for example.

In the above-mentioned conveying device, moreover, the fixed shaft maybe attached, with airtightness, to a wall portion of a vacuum chamber sothat the conveying arm assembly can be put in a vacuum environment.

Furthermore, the above-mentioned conveying device may comprise a liftmechanism for bringing the fixed shaft up and down in order to bring theconveying arm assembly up and down. In this case, the fixed shaft may beattached to a wall portion of a vacuum chamber through the liftmechanism and a flexible seal member may be provided between the fixedshaft and the wall portion of the vacuum chamber so that the conveyingarm assembly can be put in a vacuum environment.

In the above-mentioned conveying device, moreover, a statoraccommodating space isolated from an outer peripheral face of the fixedshaft may be formed in the fixed shaft, the stator being accommodated inthe stator accommodating space. According to such a structure, thestator can be put in the space isolated from the space where theoperating shafts are present. Consequently, in particular, also in thecase where the stator is attached to the vacuum chamber, the vacuumenvironment is not deteriorated.

A concave portion may be formed on the fixed shaft to be opened on theouter peripheral face of the fixed shaft and the opening of the concaveportion may be closed with airtightness by a separating wall member sothat the stator accommodating space is formed.

In the above-mentioned conveying device, furthermore, a passage forcommunicating from an end face of the fixed shaft to the statoraccommodating space may be formed in the fixed shaft. According to sucha structure, heat generated on the stator can be discharged to anoutside space through the passage. Moreover, the passage can also beutilized for distributing an electric wire to supply power to thestator.

The object as well as other objects, features and advantages of theinvention will become more apparent to those skilled in the art from thefollowing description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view showing a conveying deviceaccording to a first embodiment of the present invention;

FIGS. 2a, 2 b are views showing the appearance of the conveying device,FIG. 2a showing a state in which a conveying arm assembly is contractedand FIG. 2b showing a state in which the conveying arm assembly isexpanded;

FIG. 3 is a longitudinal sectional view showing a conveying deviceaccording to a second embodiment of the present invention;

FIGS. 4a, 4 b, 4 c, 4 d are views showing the appearance of theconveying device of FIG. 3, FIG. 4a showing a state in which bothconveying arm assemblies are contracted, FIG. 4b showing a state inwhich one of the conveying arm assemblies is expanded from the state ofFIG. 4a, FIG. 4c showing a state in which one of the conveying armassemblies is turned from the state of FIG. 4a, and FIG. 4d showing astate in which one of the conveying arm assemblies is expanded from thestate of FIG. 4c;

FIG. 5 is a longitudinal sectional view showing a conveying deviceaccording to a third embodiment of the present invention;

FIG. 6 is a longitudinal sectional view showing a conveying deviceaccording to a fourth embodiment of the present invention;

FIGS. 7a, 7 b are a longitudinal sectional views of a fixed shaftillustrating various examples of a structure for forming a statoraccommodating space, FIG. 7a showing an example in which the internalspace of the fixed shaft constituted by a cylinder member and a covermember acts as the stator accommodating space and FIG. 7b showing anexample in which a space surrounded by the inner peripheral face of thecylinder member and the outer peripheral face of a solid shaft and thelike acts as the stator accommodating space;

FIGS. 8a, 8 b are views showing the appearance of a respectivealternative conveying arm assembly according to various examples, FIG.8a showing a scalar type conveying arm assembly and FIG. 8b showing afrog—leg type conveying arm assembly;

FIG. 9 is a longitudinal sectional view showing a conveying deviceaccording to the prior art; and

FIG. 10 is a chart showing a process of controlling the rotation of ashaft.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described belowwith reference to the drawings. FIG. 1 is a longitudinal sectional viewshowing a conveying device 1A according to a first embodiment of thepresent invention. The conveying device 1A is mainly constituted by aconveying arm assembly 30, a fixed shaft 10, a set of operating shafts21 and 22, a motor M and a resolver type position detector 40. Theconveying arm assembly 30 is attached to the upper ends of the operatingshafts 21 and 22. In order to control the operation of the conveying armassembly 30, two operating shafts are required. In the presentembodiment, the two operating shafts 21 and 22 make a set to control theoperation of the conveying arm assembly 30. The lower end of the fixedshaft 10 is provided integrally with a flange portion 11. The flangeportion 11 is fixed into an attaching hole formed on a wall portion 51of a vacuum chamber 50. More specifically, the fixed shaft 10 isattached, with airtightness, to the wall portion 51 of the vacuumchamber 50 through the flange portion 11. Thus, the conveying armassembly 30 is put in a vacuum environment in the vacuum chamber 50.

The operating shafts 21 and 22 have hollow structures and are providedcoaxially with respect to the fixed shaft 10 to accommodate the fixedshaft 10 therein, that is, to be situated on the outside of the fixedshaft 10. The operating shafts 21 and 22 are rotatably attached to thefixed shaft 10 through a bearing B respectively. The operating shafts 21and 22 are attached to be piled up in a vertical direction, that is, tobe arranged in two stages in the axial direction of the fixed shaft 10.

The motor M is constituted by a permanent magnetic rotor R and anelectromagnetic stator S, and is provided between the fixed shaft 10 andeach of the operating shafts 21 and 22. The rotor R is fixed to theinner peripheral side of each of the operating shafts 21 and 22, and thestator S is provided in a position corresponding to the rotor R on theouter peripheral side of the fixed shaft 10. In the drawing, the uppermotor M serves to control the rotation of the operating shaft 21, andthe lower motor M serves to control the rotation of the operating shaft22. A concave portion 13 is formed on the fixed shaft 10. The concaveportion 13 is opened on the outer peripheral face of the fixed shaft 10and annularly takes a round of the outer periphery in thecircumferential direction of the fixed shaft 10. The opening of theconcave portion 13 is closed by a separating wall member 14. Theseparating wall member 14 has a cylindrical shape and has upper andlower ends welded to the peripheral edge of the opening of the concaveportion 13. The opening of the concave portion 13 is closed withairtightness by the separating wall member 14. Consequently, a statoraccommodating space isolated from the outer peripheral face of the fixedshaft 10 is formed. The stator S is accommodated in the statoraccommodating space.

A central hole 17 and lateral holes 18 and 19 are formed in the fixedshaft 10. The central hole 17 is formed to be opened on the lower endface of the fixed shaft 10 and to extend along the central axis of thefixed shaft 10. The lateral holes 18 and 19 are formed in the fixedshaft 10 to communicate from the central hole 17 to the concave portions13 and 15. In other words, the central hole 17 and the lateral hole 18function as a passage to communicate from the lower end face of thefixed shaft 10 to the stator S in combination with each other.Similarly, the central hole 17 and the lateral hole 19 function as apassage for communicating from the lower end face of the fixed shaft 10to an electromagnet 42 in combination with each other.

The conveying arm assembly 30 is constituted by a pulley 31, an arm 32and the like. The pulley 31 is fixed to the upper end of the operatingshaft 21, and the arm 32 is fixed to the upper end of the operatingshaft 22. While one end portion of a belt 33 is wound around the pulley31, other portion of the belt 33 is also wound around a pulley providedin the tip portion of the arm 32 which is not shown. When the rotationof the operating shaft 22 is controlled in a state in which theoperating shaft 21 is fixed, the conveying arm assembly 30 is expandedor contracted. When both the operating shafts 21 and 22 are rotated atthe same angular velocity in the same direction, the conveying armassembly 30 is turned.

The resolver type position detector 40 is constituted by a permanentmagnet 41, the electromagnet 42 and the like, and is provided betweenthe fixed shaft 10 and the operating shafts 21 and 22. The resolver typeposition detector 40 functions as a rotation detecting portion capableof detecting the rotation of each of the operating shafts 21 and 22. Theelectromagnet 42 is accommodated in the annular concave portion 15formed on the fixed shaft 10 in the same manner as the stator S. Theconcave portion 15 also has an opening closed with airtightness by acylindrical separating wall member 16.

FIGS. 2a, 2 b are views showing the appearance of the conveying device1A, FIG. 2a showing a state in which the conveying arm assembly 30 iscontracted and FIG. 2b showing a state in which the conveying armassembly 30 is expanded. An arrow Y in the drawings indicates thedirection of the turn of the conveying arm assembly 30. A work piece Wsuch as a silicon wafer or the like is mounted on a work piece conveyingportion 34 of the conveying arm assembly 30 and is moved in the vacuumchamber 50.

Referring to FIG. 1 again, both the operating shafts 21 and 22 havealmost the same shapes in the conveying device 1A. Since the fixed shaft10 is accommodated in the hollow portions of the operating shafts 21 and22, their inside diameters are comparatively increased and their outsidediameters are correspondingly increased. However, the operating shafts21 and 22 have the hollow structures and their cross-sectional shapesare annular. Therefore, it is possible to make the operating shafts 21and 22 light even if the outside diameters are large. Moreover, sincethe outside diameters are large, moduli of section can be increased andtorsional rigidities can also be enhanced. In addition, moduli ofsection and torsional rigidities of both of operating shafts 21 and 22can be increased in the conveying device 1A.

Furthermore, it is not necessary to cause one of the operating shafts topenetrate the other operating shaft differently from a conventionalconveying device. Therefore, the operating shafts 21 and 22 can becomparatively shortened. Consequently, the torsional rigidities of theoperating shafts 21 and 22 can also be enhanced.

Moreover, since the bearing B holding the operating shafts 21 and 22 isattached to the fixed shaft 10, their run-out can be reduced.

In general, a position where the rotor is provided serves as a point ofaction of the motor. In an outer rotor type motor such as the motor M ofthe conveying device 1A, it is able to cause the rotor to be moredistant from the center of rotation than in an inner rotor type motor.Accordingly, a great torque can easily be obtained. More specifically,even if the height of the rotor R (the length of the rotor R in theaxial direction of the operating shafts 21 and 22) is reduced, anecessary torque can be obtained. Therefore, the operating shafts 21 and22 can be shortened, thereby contributing to an enhancement in thetorsional rigidities of the operating shafts 21 and 22.

Generally, if a resonance is generated on the operating shaft, theprecision of positioning control of the conveying arm assembly isadversely affected. In the conveying device 1A, however, the torsionalrigidities of the operating shafts 21 and 22 can be increased asdescribed above, and the resonance frequencies of the operating shafts21 and 22 can easily be increased more than a frequency included in thedriving signal of the motor M. Consequently, the resonance of each ofthe operating shafts 21 and 22 can be prevented and the precision of thepositioning control of the conveying arm assembly 30 can be enhanced.

Moreover, the length and cross-sectional shape of each of the operatingshafts 21 and 22 can be formed almost identically with each other.Therefore, the torsional rigidity of each of the operating shafts 21 and22 can also be set almost equal with each other.

Thus, the weight of each of the operating shafts 21 and 22 can bereduced and the torsional rigidity of each of the operating shafts 21and 22 can be enhanced. Consequently, the conveying arm assembly 30 canbe quickly set in a conveying position so that it can be rapidlystabilized in the conveying position. By setting the torsionalrigidities of the operating shafts 21 and 22 equal to each other,moreover, synchronous driving can be performed at a high speed.

Furthermore, although the diameter of the operating shaft is larger thanin the conventional conveying device, the dimension of the conveyingdevice 1A is not increased because the motor M is of the outer rotortype.

As described above, moreover, the conveying device 1A has the motor M ofthe outer rotor type and it is possible to cause the rotor to be moredistant from the center of rotation in such a motor. Therefore, theoperating shafts 21 and 22 can be shortened. As a result, the height ofthe conveying device 1A can be reduced. Consequently, even if the flangeportion 11 to be fixed to the wall portion 51 of the vacuum chamber 50is formed in the vicinity of the lower end of the fixed shaft 10 as inthe conveying device 1A shown in FIG. 1, the height of projection of theconveying arm assembly 30 into the vacuum chamber 50 is sufficientlysmall. Accordingly, the driving space of the conveying arm assembly 30can be fully kept. Such a structure is advantageous to the case where anoutward projection from the wall portion 51 of the vacuum chamber 50should be reduced as much as possible.

Moreover, the stator accommodating space formed by closing the openingof the concave portion 13 with airtightness by means of the separatingwall member 14 is isolated from the outer peripheral face of the fixedshaft 10. The stator S accommodated in this space is cut off from anenvironment in which the operating shafts 21 and 22 and the conveyingarm assembly 30 are present, that is, the vacuum environment of thevacuum chamber 50. Accordingly, the vacuum environment of the vacuumchamber 50 is not deteriorated due to a dust generated on the stator Sside or the like, and a gas does not leak into the vacuum chamber 50from the stator S side.

Furthermore, a space on the periphery of the stator S and a space on theperiphery of the electromagnet 42 communicate with the air through thelateral holes 18 and 19 and the central hole 17. Consequently, heatgenerated by the stator S and the electromagnet 42 is discharged to theair. Although the concave portions 13 and 15 communicate with the airdue to the central hole 17 and the lateral holes 18 and 19, the vacuumenvironment of the vacuum chamber 50 is isolated from the air becausethe openings of the concave portions 13 and 15 are closed withairtightness by the separating wall members 14 and 16. C in the drawingdenotes an electric wire which serves to supply power to the stator Sand the electromagnet 42 and is distributed to the stator S and theelectromagnet 42 through the central hole 17 and the lateral holes 18and 19. Thus, the passage formed by the central hole 17 and the lateralholes 18 and 19 can also be utilized for the wiring to the stator S andthe electromagnet 42.

FIG. 3 is a longitudinal sectional view showing a conveying device 1Baccording to a second embodiment of the present invention. The conveyingdevice 1B has a longer fixed shaft 10B than in the conveying device 1Ashown in FIG. 1, and comprises two sets of operating shafts 21, 22, 23and 24 and two conveying arm assemblies 30 and 60 whose operations arecontrolled by the operating shafts 21, 22, 23 and 24.

The four operating shafts 21, 22, 23 and 24 have almost the same shapes,and are attached coaxially with the fixed shaft 10B to accommodate thefixed shaft 10B in their hollow spaces and to be arranged in multistagesin the axial direction of the fixed shaft 10B.

The conveying arm assembly 30 is attached to the upper ends of theoperating shafts 21 and 22, and the conveying arm assembly 60 isattached to the upper ends of the operating shafts 23 and 24. Theexpansion, contraction and turn of the conveying arm assembly 30 iscontrolled by the control of the rotation of the operating shafts 21 and22, and that of the conveying arm assembly 60 is controlled by thecontrol of the rotation of the operating shafts 23 and 24.

A motor M, the conveying arm assemblies 30 and 60 and a resolver typeposition detector 40 of the conveying device 1B have the same structuresas those in the conveying device 1A shown in FIG. 1.

FIGS. 4a, 4 b, 4 c, 4 d, are views showing the appearance of theconveying device 1B, FIG. 4a showing a state in which both the conveyingarm assemblies 30 and 60 are contracted, FIG. 4b showing a state inwhich the conveying arm assembly 60 is expanded from the state of FIG.4a, FIG. 4c showing a state in which the conveying arm assembly 30 isturned from the state of FIG. 4a, and FIG. 4d showing a state in whichthe conveying arm assembly 30 is expanded from the state of FIG. 4c.

Referring to FIG. 3 again, the conveying device 1B comprises fouroperating shafts 21, 22, 23 and 24. All the operating shafts 21, 22, 23and 24 have almost the same shapes. For all the four operating shafts21, 22, 23 and 24, weights can be reduced and torsional rigidities canbe enhanced in the same manner as in the conveying device 1A shown inFIG. 1. Moreover, the torsional rigidities of the four operating shafts21, 22, 23 and 24 can be set identically. Also in such a structure thatthe conveying arm assembly is thus attached to each set of operatingshafts, synchronous driving can be performed at a high speed and a workfor setting the conveying arm assembly in the conveying position can berapidly carried out.

As compared with the conveying device 1A shown in FIG. 1, it is apparentthat the conveying device 1B has a multishaft structure having pluralsets of operating shafts and the shape and dimension of a flange portion11B is identical to that of the flange portion 11 of the conveyingdevice 1A. This is caused by such a structure that the operating shafts21, 22, 23 and 24 are not provided coaxially but are provided inmultistages to be piled up in the axial direction of the fixed shaft10B. Thus, whether the conveying device controls the operation of onlyone conveying arm assembly or the operation of a plurality of conveyingarm assemblies, the dimension of an attaching portion can be set equaland the size of an attaching hole of a wall portion of a vacuum chamberdoes not need to be changed.

Moreover, all the operating shafts 21, 22, 23 and 24 are directly heldby bearings B attached to the fixed shaft 10B respectively. Therefore,run-out due to the precision of the bearing B is not accumulated.

FIG. 5 is a longitudinal sectional view showing a conveying device 1Caccording to a third embodiment of the present invention. The conveyingdevice 1C is different from the conveying device 1A shown in FIG. 1 inthat a rotation detecting portion capable of detecting the rotation ofoperating shafts 21C and 22C is constituted by an optical encoder 45.Other structures are almost the same as in the conveying device 1A shownin FIG. 1. Thus, not only the resolver type position detector but alsothe optical encoder can be used as the rotation detecting portion.

FIG. 6 is a longitudinal sectional view showing a conveying device 1Daccording to a fourth embodiment of the present invention. The conveyingdevice 1D is different from the conveying device 1A shown in FIG. 1 inthat it comprises a lift mechanism 70. The lift mechanism 70 is mainlyconstituted by a housing 71, a motor 72, a ball screw mechanism 73 and asupport member 74. The ball screw mechanism 73 is constituted by a screwportion 73 a and a nut portion 73 b. A flange portion 71 a is formed onthe outer periphery of the housing 71. The flange portion 71 a is fixedto an attaching hole formed on a wall portion 51 of a vacuum chamber 50.The motor 72 is accommodated in the housing 71. When the motor 72 isrotated, the screw portion 73 a coupled to the motor 72 through pulleys75 and 76 and a belt 77 is rotated. The nut portion 73 b screwed to thescrew portion 73 a is fixed to the support member 74. Accordingly, thesupport member 74 can be brought up and down by controlling the rotationof the motor 72. The upper end of the support member 74 supports thelower end of the fixed shaft 10. When the support member 74 is broughtup and down, the conveying arm assembly 30 is also brought up and down.The reference numeral 78 denotes a guide mechanism constituted by aguide column 78 a fixed to the housing 71 and a sliding portion 78 bfixed to the support member 74 for causing the guide column 78 a topenetrate.

While the fixed shaft 10 is attached to the wall portion 51 of thevacuum chamber 50 more directly through only the flange portion 11 inthe conveying device 1A shown in FIG. 1, a fixed shaft 10 is indirectlyattached to a wall portion 51 of a vacuum chamber 50 through the liftmechanism 70 in the conveying device 1D of FIG. 6. A bellows 80 which isa flexible seal member is provided between the fixed shaft 10 and thewall portion 51 of the vacuum chamber 50. The vacuum environment of thevacuum chamber 50 is kept by the bellows 80, and the conveying armassembly 30 is put in the vacuum environment. Not only the bellows 80but also the housing 71 and the support member 74 are provided betweenthe fixed shaft 10 and the wall portion 51 of the vacuum chamber 50. Allthese members function to maintain the vacuum environment of the vacuumchamber 50.

Various embodiments of the conveying device according to the presentinvention have been described with reference to FIGS. 1 to 6. In theabove-mentioned embodiments, the concave portion is formed to be openedon the outer peripheral face of the fixed shaft, and the statoraccommodating space is formed by closing the opening of the concaveportion with airtightness by means of the wall separating member. Thepassage for communicating from the end face of the fixed shaft to thestator is formed by the central hole and the lateral holes which areformed in the fixed shaft. However, the stator accommodating space canhave various structures other than the above-mentioned structures. FIGS.7a, 7 b show an example of structures other than the above-mentionedstructures for forming the stator accommodating space. FIG. 7a shows afixed shaft 10E formed by a cover member 10E1 and two cylinder members10E2 and 10E3. The cylinder members 10E2 and 10E3 are verticallyconnected such that their inner portions communicate with each other. Anopening on the upper end of the cylinder member 10E2 is closed by thecover member 10E1. A stator S is fixed to the inner peripheral faces ofeach of the cylinder members 10E2 and 10E3. In this case, an inner space17E of the fixed shaft 10E functions as a stator accommodating space.Moreover, since the space 17E communicates with the air through anopening on the lower end of the fixed shaft 10E, it also functions as apassage for the heat discharge and wiring of the stator S. FIG. 7b showsa fixed shaft 10F constituted by a cover member 10F1, a cylinder member10F2, a solid shaft 10F3, a cylinder member 10F4 and a hollow shaft10F5. The cylinder members 10F2 and 10F4 are vertically connected suchthat their inner portions communicate with each other, and an openingprovided on the upper end of the cylinder member 10F2 is closed by thecover member 10F1. Moreover, the solid shaft 10F3 and the hollow shaft10F5 are vertically connected and fixed such that they are interposedbetween the cover member 10F1 and the bottom of the cylinder member 10F4and are situated on the inside of the cylinder members 10F2 and 10F4.The hollow space of the hollow shaft 10F5 communicates with the innerspace of the cylinder member 10F4 through a hole opened on the outsideface of the hollow shaft 10F5. Furthermore, the hollow space of thehollow shaft 10F5 communicates with an air space of the outside througha hole formed in the center of the bottom of the cylinder member 10F4.The stator S is fixed to the outer peripheral faces of each of the solidshaft 10F3 and the hollow shaft 10F5. In this case, a space 17Fsurrounded by the inner peripheral faces of the cylinder members 10F2and 10F4 and the outer peripheral faces of the solid shaft 10F3 and thehollow shaft 10F5 acts as a stator accommodating space. Since the space17F communicates with the air through the hollow space of the hollowshaft 10F5 and the hole provided on the bottom of the cylinder member10F4, that is, the opening formed on the lower end of the fixed shaft10F, it also functions as a passage for the heat discharge and wiring ofthe stator S.

Moreover, the conveying arm assembly according to each of theabove-mentioned embodiments shown in FIGS. 2a, 2 b, 4 a, 4 b, 4 c and 4d are particularly an example of the conveying arm assembly forconstituting the conveying device according to the present invention,and conveying arm assemblies having various configurations can beapplied. FIGS. 8a, 8 b show another example of the conveying armassembly. FIG. 8a shows a scalar type conveying arm assembly 30G.Control for expansion, contraction and turn of the conveying armassembly 30G is performed by two operating shafts. More specifically,the conveying arm assembly 30G is expanded or contracted when one of thetwo operating shafts is fixed and the other operating shaft is rotated,and it is turned when both the operating shafts are rotated at the samerotating speed in the same direction. In the drawing, an arrow Xindicates the direction of the expansion and contraction of theconveying arm assembly 30G and an arrow Y indicates the direction of theturn of the conveying arm assembly 30G. FIG. 8b shows a frog-leg typeconveying arm assembly 30H. Control for expansion, contraction and turnof the conveying arm assembly 30H is performed by two operating shafts.The conveying arm assembly 30H is expanded or contracted when both theoperating shafts are rotated in opposite directions at the same time,and it is turned when both the operating shafts are rotated at the samerotating speed in the same direction. In the drawing, an arrow Xindicates the direction of the expansion and contraction of theconveying arm assembly 30H and an arrow Y indicates the direction of theturn of the conveying arm assembly 30H.

Moreover, in the above-mentioned embodiments, two operating shafts makeone set. However, control for operating is performed by three or moreoperating shafts depending on the kind of the conveying arm assembly. Inthat case, operating shafts required for controlling the operation ofthe conveying arm assembly make one set.

The description has been given to the embodiment in which one set ofoperating shafts are provided and the conveying arm assembly is fixed tothe upper portions of it and the embodiment in which two sets ofoperating shafts are provided and the conveying arm assembly is fixed toeach set. However, it is also possible to provide much more operatingshafts and conveying arm assemblies. Also in that case, the weight ofthe operating shaft can be reduced, and the torsional rigidity can beenhanced and set identically.

While the conveying device has been attached to the wall portion formingthe bottom face of the vacuum chamber in the above-mentionedembodiments, the conveying device can also be attached to a wall portionforming the top face of the vacuum chamber and a wall portion formingthe inner side face thereof such that the conveying arm assembly issituated in the vacuum chamber.

Although the magnetic and optical rotation detecting portions acting asthe rotation detecting portions have been described in theabove-mentioned embodiments, various other well-known detecting meanscan be used as the rotation detecting portion.

While the ball screw mechanism acting as the lift mechanism for bringingthe conveying arm assembly up and down has been described in theabove-mentioned embodiments, various well-known mechanisms such as acrank mechanism and the like can be employed as the lift mechanisms.

Numerous modifications and alternative embodiments of the invention willbe apparent to those skilled in the art in view of the foregoingdescription. Accordingly, this description is to be construed asillustrative only, and is provided for the purpose of teaching thoseskilled in the art the best mode of carrying out the invention.

What is claimed is:
 1. A conveying device comprising: a conveying armassembly; a fixed shaft; at least one set of hollow operating shafts forcontrolling an operation including at least contraction, expansion, andturning of the conveying arm assembly; and a motor provided between thefixed shaft and each of the operating shafts, wherein the one set ofoperating shafts are attached to the fixed shaft such that they can berotated coaxially with respect to the fixed shaft on an outside of thefixed shaft and are arranged in an axial direction of the fixed shaft,and the motor comprises a stator provided on the fixed shaft and a rotorprovided on each of the operating shafts such that the rotor is opposedto the stator on an outside of the stator.
 2. The conveying deviceaccording to claim 1, further comprising a plurality of conveying armassemblies and plural sets of operating shafts for controllingoperations of the conveying arm assemblies.
 3. The conveying deviceaccording to claim 1, wherein a rotation detecting portion capable ofdetecting rotation of the operating shaft is provided between the fixedshaft and the operating shaft.
 4. The conveying device according toclaim 1, wherein the fixed shaft is attached, with airtightness, to awall portion of a vacuum chamber so that the conveying arm assembly canbe put in a vacuum environment.
 5. The conveying device according toclaim 1, further comprising a lift mechanism for bringing the fixedshaft up and down in order to bring the conveying arm assembly up anddown.
 6. The conveying device according to claim 5, wherein the fixedshaft is attached to a wall portion of a vacuum chamber through the liftmechanism and a flexible seal member is provided between the fixed shaftand the wall portion of the vacuum chamber so that the conveying armassembly can be put in a vacuum environment.
 7. The conveying deviceaccording to claim 1, wherein a stator accommodating space isolated froman outer peripheral face of the fixed shaft is formed in the fixedshaft, the stator being accommodated in the stator accommodating space.8. The conveying device according to claim 7, wherein a concave portionis formed on the fixed shaft to be opened on the outer peripheral faceof the fixed shaft and the opening of the concave portion is closed withairtightness by a separating wall member, so that the statoraccommodating space is formed.
 9. The conveying device according toclaim 7, wherein a passage for communicating from an end face of thefixed shaft to the stator accommodating space is formed in the fixedshaft.